Vascular filter with sleeve

ABSTRACT

A covered vascular filter can be placed in a blood vessel, for the purpose of intercepting thrombus. The filter may be introduced to a desired site for medical treatment through a catheter which defines a lumen or passage and a distal port or opening. The filter tends to resiliently expand from a compressed shape when it is inside the catheter lumen, to an expanded shape when the filter is pushed from the catheter lumen. A cover or sleeve over those portions of the filter that would otherwise contact the vessel wall tends to reduce pressure on the vessel wall. The sleeve also tends to resist growth of the vessel wall among the elements of the filter, called endothelialization. In other words, the sleeve resists incorporation of the filter elements into the vessel wall, enabling the filter to be retrievable for a longer time. The various features of the present invention may be used singly or in any combination, as desired in a particular vascular filter.

BACKGROUND AND SUMMARY OF THE INVENTION

1. Technical Background

The present invention relates to a vascular filter with a sleevecovering, which can be temporarily or permanently placed inside a bloodvessel for the purpose of intercepting thrombus.

2. Discussion

Some basic types of vascular filters are generally known, wherein asingle filter element, mesh or member extends across the direction offlow inside a blood vessel. Several features may be desirable forvascular filters, including non-surgical or “percutaneous” delivery ofthe filter to a desired site, and expansion from a preferably smallinitial size to an expanded working size that matches the vascularanatomy at the desired site. Also, a vascular filter should preferablycapture a sufficient percentage of thrombus, while allowing blood toflow freely through the filter.

Another desirable feature is a capability to remain reliably in thedesired position in a patient's anatomy, referred to as “positionretention.” One simple attempt at position retention is to wedge avascular filter against the blood vessel wall by sizing it with adimension slightly larger than the inside diameter of the blood vessel.In addition, a vascular filter should preferably have a design wherebythe filter is self-centering and stable in the vessel, such that thefilter has a tendency not to “tilt”, which might result in lesseffective capturing of thrombus. Some vascular filters may be used inthe vena cava, and may be described in such event as a “vena cavafilter.”

A vascular filter may be delivered through a catheter in a compressedshape, the filter tending to resiliently expand within a blood vesseland to retain the desired position and orientation. The vascular filtertends to trap thrombus or particles, and resist their movement furtherdownstream. The filter includes, in a position of use, an outer shapecorresponding to the internal diameter of the blood vessel, and one ormore filter elements extending across the vessel.

In the temporal sense, there are three type of filters: (i) permanentfilters, intended for permanent implantation; (ii) temporary filters,intended for removal within a time period; and (iii) retrievablefilters, in which the physician has the option to implant the filterpermanently or to remove the filter after some time. In the case of aretrievable filter, the filter may be designed so that the physician canchoose whether to retrieve the filter at a later date, after the filterhas been in place for a while. This way, the physician can evaluate theperformance of the filter and the patient's condition, before decidingwhether to retrieve the filter or not.

To help in successful retrieval, one factor is to avoid“endothelialization” or in-growth of the vessel wall and tissue aroundthe structural members of the filter. In other words, endothelializationis the healing of the vessel inner surface by endothelial cells. It isdesirable to preserve these endothelial cells when removing aretrievable vascular filter, and the improved designs of the presentinvention tend to minimize any impact during retrieval.

On a filter, it may also be desirable to provide releasable temporaryposition stabilizers, to resist tilting and to enhance positionretention. Some vascular filters provide anchors or small barbs forimproving position retention, which extend in radial directions outwardfrom the ribs. Some filters may have barbs cut out from a centralsection of the filter. The barbs tend to gently hold the filter in placeinside the vessel.

A vascular filter along the lines of the present invention may provideseveral advantages, including effectively capturing thrombus whileallowing blood flow, resisting endothelialization of the filter, anddistributing expansive pressures of the filter to a greater area of thevessel wall. In other words, there is less stress on the vessel wall,and the sleeve enables a physician to have a longer time before choosingwhether to retrieve a retrievable filter.

A vascular filter may have an initial compressed shape, in which thefilter may have essentially a tubular shape, and may be contained in alumen or passage defined by a catheter.

After a distal tip of the catheter reaches a desired site for treatment,a wire mandrel or other deployment device may be used to push the filterout of the catheter. And when the filter is released from the catheter,it tends to resiliently expand from the initial compressed shape to anexpanded shape. When a vascular filter is retrieved from a blood vessel,the entire filter is resiliently compressed to a relatively smalldiameter, for extraction through a catheter.

A filter according to the present invention has a flexible tubularcovering on at least a portion of the filter. As a result, the filterexerts less expansive pressure on the vessel wall, and tends to resistincorporation into the vessel wall for a longer period of time.

The term “filter” will be used interchangeably, to refer to either (i) acombination device including a resilient scaffold structure with asleeve covering, or (ii) only the scaffold component, or (iii) thoseportion(s) of the scaffold which operate to capture thrombus.

The term “tubular” is used in its broadest sense, to encompass anystructure arranged a radial distance around a longitudinal axis.Accordingly, “tubular” includes any structure that (i) is cylindrical ornot, such as for example an elliptical or polygonal cross-section, orany other regular or irregular cross-section; (ii) has a different orchanging cross-section along its length; (iii) is arranged around astraight, curving, bent or discontinuous longitudinal axis; (iv) has animperforate surface, or a periodic or other perforate, irregular orgapped surface or cross-section; (v) is spaced uniformly or irregularly,including being spaced varying radial distances from the longitudinalaxis; (vi) has any desired combination of length or cross-sectionalsize.

A vascular filter may include a first and second filter section,arranged on either side of a body section. The body section and thefilter sections thus enclose a space. Due to the elongated shape of thevascular filter, and the arranging of the first and second filtersections on either side of the body member, the present filter may havean enhanced filtering effect. In other words, two opportunities havebeen created for intercepting thrombus moving inside the blood vessel.

A central tubular section tends to resiliently exert slight outwardpressure along a large section of contact area on the blood vessel wall.The sleeve distributes this outward pressure to a greater area.Accordingly, the filter tends to exert some small amount of pressure onthe internal wall of the blood vessel, and tends to hold itself inplace. The vascular filter will consequently tend not to shift position.

In addition, because of this elongated shape the vascular filter tendsto center itself within the lumen, and not to rotate transversely ortilt over.

In an example, a vascular filter may be formed out of one single piece,which provides advantages including simplicity.

When viewed along the longitudinal axis of the filter, the filtersections may have the shape of a regular polygon, and thus may provideseveral smaller filtering “cells”. The purpose of these filtering cellsis to intercept thrombus moving inside the blood vessel, and the smallerfiltering cells tend to capture more thrombus. All the cells may be ofthe same size, to provide a uniform filtering effect.

The filter sections, as arranged according to an embodiment describedabove on either side of the tubular body section, may be identical inshape, thereby enhancing the simplicity of the vascular filter accordingto the present invention.

The sleeve of the present invention may be made of any suitablematerial, and may be affixed to the filter by friction alone, or withfasteners or adhesives of any suitable type. The sleeve may be foil,and/or may be elastic or inelastic. In addition, the sleeve may bebiodegradable.

It is of course possible to build various vascular filters according tothe present invention, by various techniques and of various materials toobtain the desired features. It should be noted that the presentinvention also relates to methods for manufacturing vascular filters,and for using vascular filters for medical treatment of a patient.

These and various other objects, advantages and features of theinvention will become apparent from the following description andclaims, when considered in conjunction with the appended drawings. Theinvention will be explained in greater detail below with reference tothe attached drawings of a number of examples of embodiments of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side elevation view of a vascular filter with a sleevecovering, arranged according to the principles of the present invention;

FIG. 2 illustrates an end elevation view of the vascular filter andsleeve covering of FIG. 1;

FIG. 3 shows a perspective view of a vascular filter;

FIG. 4 shows an end elevation view of a vascular filter;

FIGS. 5 and 6 are side elevation views of vascular filters duringdeployment from a catheter;

FIG. 7 is a plan view of a vascular filter inside a blood vessel;

FIG. 8 is a plan view of a vascular filter with sleeve covering inside ablood vessel;

FIG. 9 is a perspective view of a catheter-based medical device deliverysystem; and

FIG. 10 is a partial cutaway view of a vascular filter inside a bloodvessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the presentinvention is merely illustrative in nature, and as such it does notlimit in any way the present invention, its application, or uses.Numerous modifications may be made by those skilled in the art withoutdeparting from the true spirit and scope of the invention.

The drawings depict a vascular filter medical device 10 along the linesof the present invention. The drawings depict an example vascular filtermedical device 10, which includes a filter structure 12 and a sleeve 14.Sleeve 14 is affixed to filter structure 12 in any suitable manner,including adhesives, stitching, or simply weaving sleeve 14 among themembers of filter structure 12.

Medical device 10 has an expanded shape, shown in FIGS. 1 and 2, and aninitial compressed shape, shown in FIG. 9. If medical device 10 isdelivered with a catheter 16, and a pushing wire or mandrel 18, medicaldevice 10 will have the initial compressed shape when it is within apassage or lumen of the catheter 16. In this configuration, the filter12 may have a tubular shape, and a pattern of filter members may beaffixed together or be made of a single piece of material with apatterned series of cuts.

In any event, filter 12 tends to resiliently expand from the initialcompressed shape to the expanded shape. Sleeve 14 tends to unfold asfilter 12 expands resiliently from the initial compressed shape to theexpanded shape. Once the filter 12 is in the expanded shape, it tends toresiliently maintain that expanded shape, when deployed at a desiredsite for treatment within a body passage or vessel.

The terms “filter” or “vascular filter” or “filtering” may be used in abroad or interchangeable fashion to refer generally to the entiremedical device 10, filter structure 12, the first and second filteringsection 22 and 24, the filtering effect on body fluids or particulates,or the results of such a filtering effect, or any other relevant aspectof the present invention.

Structurally, filter 12 has a central section 20, flanked by a first andsecond filtering section 22 and 24, which are flanked by a first andsecond end 26 and 28. The particular example depicted in the drawings ismade from a single piece of tubular material, with a patterned series ofcuts, which is treated to resiliently expand and form the filtering meshstructure. The filter structure could of course also be formed ofmultiple members which are affixed together.

Sleeve 14 may have a generally tubular or annular structure, such thatwhatever configuration or shape may be selected for the sleeve, itencircles all or a portion of filter 12 around its longitudinal axis.Sleeve 14 may be made of a foil, film or a metal or polymer material.Also, sleeve 14 may be made of elastic or inelastic material. Inaddition, sleeve 14 may also be made of biodegradable material.

The sleeve tends to distribute expansive pressures of the members offilter 12 to a greater portion of an inner wall of a body passage orvessel in which the medical device 10 is implanted.

While the medical device 10 is implanted within a patient, body tissuesnaturally tend to incorporate or endothelialize implanted objects. Thisprocess of endothelialization may take place over a predictable periodof time, and when a filter or other medical device has been incorporatedor endothelialized, it may be preferred to leave it in placeindefinitely. Sleeve 14 may tend to extend this period of time ofincorporation, allowing medical filter 10 to remain in place and providetherapeutic benefit for a longer period of time, yet continue to beretrievable.

If the medical device is intended to be a temporary or a retrievablefilter, such that the filter may be removed or retrieved at a latertime, the filter may be provided with features advantageous to suchpossible retrieval. For example, filter 12 may have on one or both endsa hook or loop construction, such as for example retrieval hook 30. Hook30 may be used to extract the medical device 10 back into a catheter bymeans of a cooperating hook, snare or grabbing member.

In the compressed shape when the vascular filter is inside the catheter,the filter may include cuts extending in the longitudinal direction ofthe filter between, but not as far as, the ends of the filter. The cutsdefine strips of material as illustrated in the drawings. These stripsexpand to form the filtering first and second mesh. The specific cutsconsequently also form the filter elements 22 and 24 on either side ofthe filter 12. The strips extend in a generally longitudinal direction.

The vascular filter 12 embodiment illustrated here may of course be usedin the vena cava or any other desired site for treatment. The filter 12preferably includes a number of ribs extending in a longitudinaldirection along the internal wall of the blood vessel or body passage.These ribs together form central body section 20. Each filter section 22and 24 form a grid shape. Liquid inside the blood vessel can passthrough the vascular filter 12, but thrombus or particulates tend to beintercepted by one of the two filter sections 22 or 24.

Another advantage of this configuration is that it provides two filterelements for intercepting thrombus moving inside the blood vessel. Inaddition, due to the sleeve and the filter shape, the filter providesless possibility for any trauma to a vessel.

As the filter sections 22 and 24 have been arranged on either side ofthe central body of the filter, a longitudinally symmetrical shape hasbeen obtained (except for hook 30). There is no difference whether thevascular filter is placed forward or backward inside the blood vessel.In other words, the proximal and distal ends of the filter are identicaland symmetrical. Accordingly, a single pre-loaded catheter system may beused to deploy a filter at a desired site, from either an upstream ordownstream direction.

In the axial view of FIG. 3, the filter sections on either side of theribs of the vascular filters according to the present inventiondescribed above display diamond or polygon shapes. It is also possibleto provide vascular filters of which the filter sections display inaxial view a star shape, or any other suitable shape, as long as theysuccessfully intercept blood clots or thrombus. An advantage of thisfeature is that, after passing the first filter section 28 and thetubular section or the elongated body member, a second filter element 30for intercepting thrombus has been provided. Also, other shapes of thefilter sections in axial view are possible, which shapes will occur tothose skilled in the field after reading the present description. Theshapes of the filter sections in axial view need not be symmetrical, andmay in principle have any suitable appearance.

As shown in the drawings, the filter 12 preferably has one or more barbsor anchors 32, located on one or more of the longitudinal ribs. Theanchors 32 may be positioned at one or both ends of the longitudinalribs, and may be directed in the proximal or distal directions. Asshown, opposing sets of proximal and distal anchors 32 may be arrangedto face in both longitudinal directions respectively. This opposingarrangement causes the anchors 32 to resist movement of the filter 12 inboth longitudinal directions.

The filter 12 may for example be delivered to the vascular region in thegeneral area of the heart from either a femoral artery access point inthe leg, or a jugular artery access point in the neck. Because thefilter shown in FIG. 2 is longitudinally symmetrical, the same filterdelivery system 10 may be used for either femoral or jugular access,because the opposing sets of anchors 32 will resist downstream migrationof the filter, regardless of the longitudinal orientation of the filter.

Furthermore, retraction of a vascular filter according to the presentinvention is mentioned above, which should not limit the scope of theclaims attached. Regarding the subject of the invention, it is thereforeof no consequence whether the filter is placed permanently, in aremovable manner, temporarily or otherwise.

In addition to the nitinol mentioned so far, many other materials mayalso be used for manufacturing a vascular filter according to thepresent invention. By way of alternative, various metals may forinstance be used, including stainless steel. In any case, the vascularfilter preferably tends to resiliently assume the intended shape afterhaving been ejected from the catheter.

Vascular filters according to the present invention may be made of anysuitable material using a variety of methods. One material having thedesired characteristics of strength, resilience, flexibility,biocompatibility and endurance is nitinol. Other possible materialsinclude stainless steel and any other material having the desiredproperties.

Likewise, the manufacturing methods for the filter of the presentinvention may include providing a tube, and then cutting a pattern intothe tube to enable expansion into the desired shape. Various othermethods are of course possible, including forming the filter of discretemembers and joining or connecting the members, or chemically etching asubstrate. The manufacturing methods may include an inflatable orexpandable mold, heating or cooling, welding, etc.

In FIG. 9, a medical device 10 is loaded into a catheter 16 lumen whichextends from a proximal end having a hub to a distal opening. At leastone vascular filter 12 is preferably arranged, in a compressed state, inthe distal end of the catheter. The filter 12 is then pushed out thecatheter distal opening by a flexible pushing wire 18.

In an alternative embodiment, it is also possible that the filter 12 maybe inserted at the proximal end of the catheter 16, and then pushedalong the entire length of the catheter 16 by the pushing wire 18, afterthe catheter distal end 20 has been advanced to the desired position.

In any event, when the vascular filter 12 is ejected by the pushing wire18 out from the distal tip of the catheter 16 into the blood vessel, thevascular filter 12 will tend to resiliently expand after being releasedfrom the catheter 16. The material and design of the filter 12 resultsin resilient expansive forces that tend to cause the vascular filter 12to take the illustrated shape.

It should be understood that an unlimited number of configurations forthe present invention could be realized. The foregoing discussiondescribes merely exemplary embodiments illustrating the principles ofthe present invention, the scope of which is recited in the followingclaims. Those skilled in the art will readily recognize from thedescription, claims, and drawings that numerous changes andmodifications can be made without departing from the spirit and scope ofthe invention.

1. A medical device for therapeutic treatment of a patient, comprising:a filter having a first and second end, and a central expandable portionextending between the ends; the central portion tending to resilientlyexpand in radially outward directions from a compressed initial shape toan expanded deployed shape; wherein the filter defines a first andsecond filtering element in the expanded shape, the first and secondfiltering elements each being near the first and second end,respectively; the filter having a plurality of ribs arranged in apre-selected pattern; such that the ribs expand in radially outwarddirections when the filter expands from the compressed shape to theexpanded shape, thereby causing the first and second ends to move towardeach other and; a flexible sleeve encircling at least a portion of thefilter, around a longitudinal axis defined between the first and secondends; the sleeve defining a surface area; the sleeve tending to expandwith the filter central portion to an expanded shape in which the sleeverepresents a tubular surface for contracting a blood vessel wall.
 2. Themedical device of claim 1, wherein the sleeve is made of foil.
 3. Thevascular filter as set forth in claim 1, wherein the sleeve tends toreduce pressure imparted by the filter on a blood vessel wall.
 4. Themedical device of claim 1, wherein the sleeve is made of biodegradablematerial.
 5. The medical device of claim 1, wherein the sleeve extends atime in which the medical device is endothelialized into the bloodvessel wall.
 6. The medical device of claim 1, wherein the sleeve ismade of elastic material.
 7. The medical device of claim 1, wherein thesleeve is made of inelastic material.
 8. The medical device of claim 1,wherein the filter is retrievable and has a retrieval member.
 9. Amedical system for therapeutic treatment of a patient, comprising: afilter with a sleeve, a catheter, and a pushing wire; the filter havinga first and second end, and a central expandable portion extendingbetween the ends; the central portion tending to resiliently expand inradially outward directions from a compressed initial shape to anexpanded deployed shape; wherein the filter defines a first and secondfiltering element in the expanded shape, the first and second filteringelements each being near the first and second end, respectively; thefilter having a plurality of ribs arranged in a pre-selected pattern;such that the ribs expand in radially outward directions when the filterexpands from the compressed shape to the expanded shape, thereby causingthe first and second ends to move toward each other and; a flexiblesleeve encircling at least a portion of the filter, around alongitudinal axis defined between the first and second ends; the sleevedefining a surface area; the sleeve tending to expand with the filtercentral portion to an expanded shape in which the sleeve represents atubular surface for contracting a blood vessel wall; and the catheterhaving a proximal and distal end, and a defining a lumen extendingbetween the proximal and distal ends; the pushing wire being insertedwithin the lumen; wherein the filter and sleeve are within the lumen ofthe catheter in the initial compressed shape.